(a) Field of the Invention
The present invention relates to a vacuum cleaner comprising a fuzzy inferring device for reducing the sudden change of the number of rotations of a motor accommodated in the vacuum cleaner.
(b) Description of the Related Arts
In recent years, with the variety of objects such as a carpet to be cleaned, vacuum cleaners in which the number of rotations of a motor can be varied are increasingly manufactured. As the main current of the production of vacuum cleaners, a dust sensor is provided to control the number of rotations of the motor according to the amount of dust.
Conventionally, a vacuum cleaner of this kind has a construction as shown in FIG. 7. The construction of the vacuum cleaner is described below.
As shown in FIG. 7, a dust sensor 1 outputs pulse signals to a dust amount detecting means 2 when dust passes therethrough. The dust amount detecting means 2 counts pulse signals per unit time. A means 3 for setting the number of rotations sets the number of rotations of a motor 4. In response to the output of the motor 4, a control means 5 controls the rotation of the motor 4.
As shown in FIG. 8, the sensor 1 comprises a light emitting element 6 and a light receiving element 7. When light emitted by the light emitting element 6 is intercepted by dust which is passing between the light emitting element 6 and the receiving element 7, the intensity of light received by the receiving element 7 changes. The light receiving element 7 converts the change of the intensity of the light, thus outputting pulse signals.
Referring to FIGS. 9A and 9B, the operation of the means 3 for setting the number of rotations of the motor 4 is described below.
As shown in FIG. 9A, when the sensor 1 detects dust 8, the number of rotations of the motor 4 is set in correspondence with the amount of dust 8 as shown in Fig. 9B. When no dust is detected, the number of rotations of the motor 4 is set to n.sub.1. When the amount of dust 8 is greater than d.sub.1, the number of rotations of the motor 4 is set to n.sub.3. When the amount of dust 8 is smaller than d.sub.1, the number of rotations of the motor 4 is set to n.sub.2.
According to the above-described vacuum cleaner, since the number of rotations of the motor 4 is successively varied according to the amount of dust 8 within unit time, it frequently occurs that the number of rotations of the motor 4 suddenly changes when the dust 8 is being intermittently detected. Consequently, the volume of sounds generated by the vacuum cleaner change suddenly. Thus, the conventional vacuum cleaner has problems in operation.